Di2 Battery Holder for 25.4 mm Seat Posts


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This battery holder is for Shimano Di2 internal SM-BTR2 and BT-DN110 batteries. The battery fits inside the seat post and typically requires a seat post made specifically for Di2. This holder allows the battery to be held securely within a non-Di2 specific 25.4mm seat post found on many bikes from 2014 to present. It will also fit other seat posts with the same inside diameter.

Made from hard, tough, and tear resistant rubber.  Completely protects the delicate battery connector.

Collections: Di2-eTAP Conversion Accessories

Battery Holder Sizes

We make Di2 battery holders for 25.4mm seat posts with various inside diameter size options primarily for Cannondale seat posts.  If you are using a non-Cannondale or FSA seat post, measure the inside diameter with a caliper and round up.  If the measurement is more than .25 mm from the available sizes, or an odd shape, contact us for assistance.

Seat Post Sizes:

Cannondale Branded

C2 - 19 mm ID

C3 - 19.5 mm ID

FSA Branded

SL-K - 20.5 mm ID

Why use a holder instead of tape or foam?

Ad hoc solutions using tape and foam have multiple issues. The net result is often a damaged or stuck battery.

Problems with Tape or Foam:

  • They don't protect the delicate battery connection
  • Tape or foam can shrink, causing the battery to fall out
  • They can cause the battery to overheat
  • Tape, especially, can fuse to the inside of the seat post


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